Well if you only a level 9 you still have a long ways to go but it's good to be thinking ahead. In my oppinion it would be good to learn both and both are very helpful. My mistake was not learning and wasting my training points so now I have to get more to go back and learn all of the spells.
Well, as ice, it seems you will need Gargantuan and amplify (for damage) though infallible (I don't know how to spell it) is pretty good too. The only school spell I would suggest learning is a fire polymorph, so that you don't need too many prisms to beat an enemy. Anyways, gargantuan is and infallible and amplify are . But, don't be thinking too far ahead! You still have AT LEAST 39 more levels to go through before you get to those!
I would suggest training the Star spells Amplify, Infallible, Vengeance and Conviction. If you make it to Azteca I would recommend Sleet Storm from Star spells. Also you should also train all the Sun spells that increase your damage (Strong, Giant, Monstrous, Gargantuan, Colossal.) Also if you make it to Azteca I would also recommend Sharpen Blade from Sun spells.